Whole-watershed mercury balance at Sagehen Creek, Sierra Nevada, CA

Faïn, Xavier; Obrist, Daniel; Pierce, Ashley M.; Barth, C. L.; Gustin, Mae Sexauer; Boyle, Douglas P.

doi:10.1016/j.gca.2011.01.041

Cited by 27 publications

(27 citation statements)

References 57 publications

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“…4) is not efficiently scavenged by snow. However, questions remain as to the MDN collection efficiency of snow (Sanei et al, 2010;Faïn et al, 2011). We have used long-term measurements of RGM and PBM at five sites in North America to derive an empirical gas-particle Hg(II) partitioning coefficient as a function of PM 2.5 and temperature: log 10 (K −1 ) = (10±1)-(2500±300)/T where K = (PBM/PM 2.5 )/RGM, PBM and RGM are in common mixing ratio units, PM 2.5 is in µg m −3 , and T is in K. Implementation of this Hg(II) gas-particle partitioning in the global 3-D GEOS-Chem Hg model yields Hg(II) fractions in the particle phase ranging from more than 90 % in cold air masses with high aerosol burdens to less than 10 % in warm air with low aerosol.…”

Section: Implications For Hg Depositionmentioning

confidence: 99%

Gas-particle partitioning of atmospheric Hg(II) and its effect on global mercury deposition

Amos

Jacob²,

Holmes³

et al. 2012

Atmos. Chem. Phys.

412

459

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Abstract. Atmospheric deposition of Hg(II) represents a major input of mercury to surface environments. The phase of Hg(II) (gas or particle) has important implications for deposition. We use long-term observations of reactive gaseous mercury (RGM, the gaseous component of Hg(II)), particle-bound mercury (PBM, the particulate component of Hg(II)), fine particulate matter (PM 2.5 ), and temperature (T ) at five sites in North America to derive an empirical gas-particle partitioning relationship log 10 (K −1 ) = (10±1)-(2500±300)/T where K = (PBM/PM 2.5 )/RGM with PBM and RGM in common mixing ratio units, PM 2.5 in µg m −3 , and T in K. This relationship is within the range of previous work but is based on far more extensive data from multiple sites. We implement this empirical relationship in the GEOS-Chem global 3-D Hg model to partition Hg(II) between the gas and particle phases. The resulting gas-phase fraction of Hg(II) ranges from over 90 % in warm air with little aerosol to less than 10 % in cold air with high aerosol. Hg deposition to high latitudes increases because of more efficient scavenging of particulate Hg(II) by precipitating snow. Model comparison to Hg observations at the North American surface sites suggests that subsidence from the free troposphere (warm air, low aerosol) is a major factor driving the seasonality of RGM, while elevated PBM is mostly associated with high aerosol loads. Simulation of RGM and PBM at these sites is improved by including fast in-plume reduction of Hg(II) emitted from coal combustion and by assuming that anthropogenic particulate Hg(p) behaves as semivolatile Hg(II) rather than as a refractory particulate component. We improve the simulation of Hg wet deposition fluxes in the US relative to a previous version of GEOS-Chem; this largely reflects independent improvement of the washout algorithm. The observed wintertime minimum in wet deposition fluxes is attributed to inefficient snow scavenging of gas-phase Hg(II).

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Section: Implications For Hg Depositionmentioning

confidence: 99%

Gas-particle partitioning of atmospheric Hg(II) and its effect on global mercury deposition

Amos

Jacob²,

Holmes³

et al. 2012

Atmos. Chem. Phys.

412

459

View full text Add to dashboard Cite

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“…For example, ionic pulses of anions and cations occur upon snowpack melt, whereby ions are thought to be mobilized in the following order: SO (Berg, 1992;Brooks and Williams, 1999;Kuhn, 2001;Stottlemyer and Rutkowski, 1990;Williams and Melack, 1991b). In addition, pollutants such as Hg and persistent organic pollutants (POPs) as well as nutrients can undergo photochemical transformations and be subject to substantial gaseous re-emission to the atmosphere (Fain et al, 2011;Halsall, 2004;Lalonde et al, 2002;Poulain et al, 2007). Specific examples include photochemical reduction and re-emission of mercury (Hg) during snowpack storage as well as photolysis and emission of nitrate (NO − 3 ) from polar snow (Galbavy et al, 2007;Jacobi and Hilker, 2007;Rothlisberger et al, 2002).…”

Section: Pearson Et Al: Nutrient and Mercury Deposition And Storamentioning

confidence: 99%

“…Such different precipitation patterns can cause large differences in wet deposition across mountain ranges (Fain et al, 2011;NADP, 2012). Assessing spatial deposition patterns using snowpack sampling at multiple locations across a watershed should allow for better characterization of basin-wide deposition patterns as well as assessment of impacts of nearby urban areas versus regional and global sources of atmospheric deposition (Brown et al, 2011;Kuhn, 2001;Morales-Baquero et al, 2006;Vicars and Sickman, 2011).…”

Section: Pearson Et Al: Nutrient and Mercury Deposition And Storamentioning

confidence: 99%

“…The lack of spatial trends suggests global background atmospheric pollution, rather than specific point sources such as urban areas, to be the main source of snowpack Hg in the Lake Tahoe Basin. Mercury's long atmospheric lifetime and global circulation allow for diffuse deposition to this relatively remote mountain region (Fain et al, 2011;Schroeder and Munthe, 1998), and the majority of large snowfall events in the Sierra Nevada originate as large-scale convection cells in the eastern Pacific and travel hundreds of kilometers before reaching the Tahoe Basin (O'Hara et al, 2009). To our knowledge, few point sources for Hg emission exist within the Lake Tahoe Basin, although one study within the basin reported that significant amounts of particulate Hg are emitted from wildfires (Zhang et al, 2013) and found increased levels of particulate Hg in urban areas of the Lake Tahoe Basin.…”

Section: Phosphorusmentioning

confidence: 99%

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Nutrient and mercury deposition and storage in an alpine snowpack of the Sierra Nevada, USA

et al. 2015

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Abstract. Biweekly snowpack core samples were collected at seven sites along two elevation gradients in the Tahoe Basin during two consecutive snow years to evaluate total wintertime snowpack accumulation of nutrients and pollutants in a high-elevation watershed of the Sierra Nevada. Additional sampling of wet deposition and detailed snow pit profiles were conducted the following year to compare wet deposition to snowpack storage and assess the vertical dynamics of snowpack nitrogen, phosphorus, and mercury. Results show that, on average, organic N comprised 48 % of all snowpack N, while nitrate (NO − 3 -N) and TAN (total ammonia nitrogen) made up 25 and 27 %, respectively. Snowpack NO − 3 -N concentrations were relatively uniform across sampling sites over the sampling seasons and showed little difference between seasonal wet deposition and integrated snow pit concentrations. These patterns are in agreement with previous studies that identify wet deposition as the dominant source of wintertime NO − 3 -N deposition. However, vertical snow pit profiles showed highly variable concentrations of NO − 3 -N within the snowpack indicative of additional deposition and in-snowpack dynamics. Unlike NO − 3 -N, snowpack TAN doubled towards the end of winter, which we attribute to a strong dry deposition component which was particularly pronounced in late winter and spring. Organic N concentrations in the snowpack were highly variable (from 35 to 70 %) and showed no clear temporal, spatial, or vertical trends throughout the season. Integrated snowpack organic N concentrations were up to 2.5 times higher than seasonal wet deposition, likely due to microbial immobilization of inorganic N as evident by coinciding increases in organic N and decreases in inorganic N in deeper, aged snow. Spatial and temporal deposition patterns of snowpack P were consistent with particulate-bound dry deposition inputs and strong impacts from in-basin sources causing up to 6 times greater enrichment at urban locations compared to remote sites. Snowpack Hg showed little temporal variability and was dominated by particulate-bound forms (78 % on average). Dissolved Hg concentrations were consistently lower in snowpack than in wet deposition, which we attribute to photochemically driven gaseous re-emission. In agreement with this pattern is a significant positive relationship between snowpack Hg and elevation, attributed to a combination of increased snow accumulation at higher elevations causing limited light penetration and lower photochemical re-emission losses in deeper, higher-elevation snowpack. Finally, estimates of basin-wide loading based on spatially extrapolated concentrations and a satellite-based snow water equivalent reconstruction model identify snowpack chemical loading from atmospheric deposition as a substantial source of nutrients and pollutants to the Lake Tahoe Basin, accounting for 113 t of N, 9.3 t of P, and 1.2 kg of Hg each year.

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“…For example, precipitation amounts may directly lead to changes in wet deposition loads (NADP, 2011) leading to changes in soil Hg densities (although such effects may be highly nonlinear due to "washout" effects (Lamborg et al, 1995;Landis et al, 2002;Lyman and Gustin, 2008;Mason et al, 1997;Faïn et al, 2011). Further, correlations between annual precipitation and soil Hg may be caused by canopy wash-off and throughfall deposition which in forest ecosystems is a significant deposition flux (Demers et al, 2007;Rea et al, 1996;Graydon et al, 2008a), and such deposition loads likely would be efficiently retained in ecosystems (e.g., soils generally retain more than 90 % of Hg deposited with rainfall; Ericksen et al, 2005;Harris et al, 2007;Graydon et al, 2009;Hintelmann et al, 2002).…”

Section: Sensitivity To Precipitation Changesmentioning

confidence: 99%

Modelling the sensitivity of soil mercury storage to climate-induced changes in soil carbon pools

2013

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Substantial amounts of mercury (Hg) in the terrestrial environment reside in soils and are associated with soil organic carbon (C) pools, where they accumulated due to increased atmospheric deposition resulting from anthropogenic activities. The purpose of this study was to examine potential sensitivity of surface soil Hg pools to global change variables, particularly affected by predicted changes in soil C pools, in the contiguous US. To investigate, we included a soil Hg component in the Community Land Model based on empirical statistical relationships between soil Hg / C ratios and precipitation, latitude, and clay; and subsequently explored the sensitivity of soil C and soil Hg densities (i.e., areal-mass) to climate scenarios in which we altered annual precipitation, carbon dioxide (CO₂) concentrations and temperature.

Our model simulations showed that current sequestration of Hg in the contiguous US accounted for 15 230 metric tons of Hg in the top 0–40 cm of soils, or for over 300 000 metric tons when extrapolated globally. In the simulations, US soil Hg pools were most sensitive to changes in precipitation because of strong effects on soil C pools, plus a direct effect of precipitation on soil Hg / C ratios. Soil Hg pools were predicted to increase beyond present-day values following an increase in precipitation amounts and decrease following a reduction in precipitation. We found pronounced regional differences in sensitivity of soil Hg to precipitation, which were particularly high along high-precipitation areas along the West and East Coasts. Modelled increases in CO₂ concentrations to 700 ppm stimulated soil C and Hg accrual, while increased air temperatures had small negative effects on soil C and Hg densities. The combined effects of increased CO₂, increased temperature and increased or decreased precipitation were strongly governed by precipitation and CO₂ showing pronounced regional patterns. Based on these results, we conclude that the combination of precipitation and CO₂ should be emphasised when assessing how climate-induced changes in soil C may affect sequestration of Hg in soils

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Whole-watershed mercury balance at Sagehen Creek, Sierra Nevada, CA

Cited by 27 publications

References 57 publications

Gas-particle partitioning of atmospheric Hg(II) and its effect on global mercury deposition

Gas-particle partitioning of atmospheric Hg(II) and its effect on global mercury deposition

Nutrient and mercury deposition and storage in an alpine snowpack of the Sierra Nevada, USA

Modelling the sensitivity of soil mercury storage to climate-induced changes in soil carbon pools

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